1. Field
Embodiments of the invention relate to the field of networking; and more specifically, to multicast traffic processing.
2. Background
Multicast routing allows a source to send packets (e.g., a multicast traffic stream) to any number of destinations. Thus, multicast routing is a one-to-any routing scheme. The destinations decide whether to join the multicast traffic stream. Thus, the source may communicate with more than one destination within a network without the source separately addressing traffic to each destination on the network that joined the multicast traffic stream.
Protocol Independent Multicast (PIM) is a multicast routing protocol that runs over existing unicast (one-to-one routing scheme) architectures. There are several variants of PIM routing protocols (e.g., PIM Sparse Mode (defined in Request for Comments (RFC) 4601, August 2006), PIM Dense Mode (defined in RFC 3973, January 2005), and PIM Source Specific Mode (defined in RFC 3569, July 2003)). In each variant, PIM makes use of a unicast routing protocol to populate routing tables and uses those tables during multicast processing. For example, a unicast routing protocol typically determines a best route towards the multicast traffic source and PIM uses this route. PIM also relies on the Internet Group Management Protocol (IGMP) (defined in RFC 1112, RFC 2236, and RFC 3376) to provide the multicast group membership information. IGMP is typically used by the local multicast receivers (or local customer premise equipment) that desire to join a multicast traffic stream.
In a typical prior art technique implementing PIM, multicast traffic is received at a single interface of a network element that joined the multicast traffic (e.g., the interface chosen by the unicast routing protocol as having the best route towards the multicast traffic source). For example, in an IP multicasting prior art technique the multicast traffic is received on one IP interface of a network element that joined the multicast traffic as chosen by the unicast routing protocol operating on that network element (e.g., Interior Gateway Protocol (IGP)).